Brakes for electric railway cars (hereinafter referred to as electric cars) include electric brakes, which obtain brake force by causing an electric motor to operate as an electric generator, and mechanical brakes, which obtain brake force due to friction generated by using air pressure or hydraulic pressure to push a brake shoe against the tread of the wheel, or push a pad against a brake disc. Control devices for electric cars that implement both electric brakes and mechanical brakes are being used in practical applications.
In a control device for an electric car that implements both electric brakes and mechanical brakes, a required brake force for a vehicle is computed based on the load on the vehicle and a brake command given from the driver's cab or the like, and the electric brakes operate within a range determined by a limit value of the overhead line voltage, for example. When the brake force of the electric brakes is less than the required brake force, the brake force is supplemented by the mechanical brakes. This is called air supplement control.
As the overhead line voltage rises, changes in the overhead line voltage limit occur frequently. For this reason, the electric car control device disclosed in Patent Literature 1 decreases fluctuations in the air supplement control due to changes in the overhead line voltage limit, and minimizes fluctuations in the wear loss of the brake shoes.